首页 \ 问答 \ HttpClient提供的不是真正的异步操作吗？(HttpClient provide not truly async operations?)

HttpClient提供的不是真正的异步操作吗？(HttpClient provide not truly async operations?)

 我对异步IO操作感到困惑。 在本文中， Stephen Cleary解释说我们不应该使用Task.Run(() => SomeIoMethod())因为真正的异步操作应该使用 
 

 
 
 .NET中的标准P / Invoke异步I / O系统 
 

 

 http://blog.stephencleary.com/2013/11/there-is-no-thread.html 
 

 
 
 但是，避免库中的“伪异步”。 假异步是指组件具有异步就绪API，但它是通过将同步API包装在线程池线程中来实现的。 这对ASP.NET的可伸缩性起反作用。 假异步的一个突出例子是Newtonsoft JSON.NET，这是一个非常出色的库。 最好不要调用（假的）异步版本来序列化JSON; 只需调用同步版本。 虚假异步的一个棘手的例子是BCL文件流。 打开文件流时，必须显式打开它以进行异步访问; 否则，它将使用伪异步，同步阻塞文件读写线程池线程。 
 

 

 他建议使用HttpClient但内部使用Task.Factory.StartNew() 在此处输入图像描述 
 

 这是否意味着HttpClient不提供真正的异步操作？ 

I'm confused about async IO operations. In this article Stephen Cleary explains that we should not use Task.Run(() => SomeIoMethod()) because truly async operations should use 
 

 
 
standard P/Invoke asynchronous I/O system in .NET
 

 

http://blog.stephencleary.com/2013/11/there-is-no-thread.html
 

 
 
However, avoid “fake asynchrony” in libraries. Fake asynchrony is when a component has an async-ready API, but it’s implemented by just wrapping the synchronous API within a thread pool thread. That is counterproductive to scalability on ASP.NET. One prominent example of fake asynchrony is Newtonsoft JSON.NET, an otherwise excellent library. It’s best to not call the (fake) asynchronous versions for serializing JSON; just call the synchronous versions instead. A trickier example of fake asynchrony is the BCL file streams. When a file stream is opened, it must be explicitly opened for asynchronous access; otherwise, it will use fake asynchrony, synchronously blocking a thread pool thread on the file reads and writes.
 

 

And he advises to use HttpClient but internaly it use Task.Factory.StartNew() enter image description here
 

Does this mean that HttpClient provides not truly async operations?

原文：https://stackoverflow.com/questions/39931213
更新时间：2023-06-15 16:06

最满意答案

 在MonthView Change Weeks中显示为3也会在委托方法setBeginingofmonth中注释以下代码 
 

 for(JTCalendarWeekView *view in weeksViews)
{
    view.currentMonthIndex = currentMonthIndex;
    [view setBeginningOfWeek:currentDate];

    NSDateComponents *dayComponent = [NSDateComponents new];
    dayComponent.day = 7;

    currentDate = [calendar dateByAddingComponents:dayComponent toDate:currentDate options:0];

    // Doesn't need to do other weeks
//        if(self.calendarManager.calendarAppearance.isWeekMode)
//        {
//            break;
//        }
    }

 

 在JTCalendar updatePage方法中，如下所示更改7到14 
 

 if(!self.calendarAppearance.isWeekMode)
{
    dayComponent.month = currentPage - (NUMBER_PAGES_LOADED / 2);
}
else
{
    //to show next starting week for two weeks mode put 14
    dayComponent.day = 14 * (currentPage - (NUMBER_PAGES_LOADED / 2));
}


In MonthView Change Weeks to display as 3 also do this comment the following code in delegate method setBeginingofmonth
 

 for(JTCalendarWeekView *view in weeksViews)
{
    view.currentMonthIndex = currentMonthIndex;
    [view setBeginningOfWeek:currentDate];

    NSDateComponents *dayComponent = [NSDateComponents new];
    dayComponent.day = 7;

    currentDate = [calendar dateByAddingComponents:dayComponent toDate:currentDate options:0];

    // Doesn't need to do other weeks
//        if(self.calendarManager.calendarAppearance.isWeekMode)
//        {
//            break;
//        }
    }

 

in JTCalendar updatePage method change 7 to 14 as below
 

 if(!self.calendarAppearance.isWeekMode)
{
    dayComponent.month = currentPage - (NUMBER_PAGES_LOADED / 2);
}
else
{
    //to show next starting week for two weeks mode put 14
    dayComponent.day = 14 * (currentPage - (NUMBER_PAGES_LOADED / 2));
}

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